The present invention relates to a sulfur-carbon composite comprising a highly graphitic carbon material for lithium-sulfur batteries, an electrode and a lithium-sulfur battery comprising said composite as well as a process for preparing said sulfur-carbon composite.
Lithium-Sulfur batteries are nowadays undergoing a tremendous number of investigations due to the highly theoretical energy density of 2600 Wh kg−1. However, Li—S batteries are still suffer from poor cycling life and rate performance due to the intrinsic insulate sulfur/lithium sulfides and dissolution of intermediate polysulfide species for irreversible loss. Porous carbon is proven as an effective matrix in trapping polysulfides within pore structures, hence enhancing the capacity retention capability. Highly graphitic carbon materials, which always require an intense preparation condition, benefit for enhancing electro-activity of sulfur, and facilitating transportation of electrons and ions. Different porous carbon had been designed to accommodate sulfur, however, integrating all the structural benefits such as ample space, highly graphitic domains, interconnected ion channels, and confined nanospace with a facile approach to utilize and immobilize sulfur has still not been fully demonstrated.
To provide good electronic conductive network and confine polysulfide intermediates, porous carbon framework with a certain degree of graphitization has been used as an effective matrix to immobilize sulfur. However, current synthetic methods are usually complex, and the degree of graphitization of these porous carbon materials is very low, which lies as big obstacle for achieving highly cycling stability and highly-rate capability.